1. Technical Field
The present invention relates generally to an improved data processing system and, in particular, to a method and system for monitoring performance of the processor in a data processing system when an interrupt occurs. Still more particularly, the present invention relates to a method, apparatus, and computer instructions for providing pre handlers and post handlers to record events.
2. Description of Related Art
A typical data processing system utilizes processors to execute a set of instructions in order to perform a certain task, such as reading a specific character from the main memory. However, as the number of tasks required to be executed by the processor increases, the efficiency of the processor's access patterns to memory and the characteristics of such access become important factors for engineers who want to optimize the system.
Currently, the prior art contains mechanisms that can count occurrences of software-selectable events, such as, for example, cache misses, instructions executed, I/O data transfer request, and the time a given process may take to execute within a data processing system. One such mechanism is a performance monitor. A performance monitor monitors selected characteristics for system analysis by determining a machine's state at a particular time. This analysis provides information of how the processor is used when instructions are executed and its interaction with the main memory when data is stored. This analysis may also be used to determine if application code changes, such as a relocation of branch instructions and memory access, to further optimize the performance of a system are necessary. In addition, the performance monitor may provide the amount of time that has passed between events in a processing system. The performance monitor counts events that may be used by engineers to analyze system performance. Moreover, data regarding how the processor accesses the data processing system's level 1 and level 2 cache, and main memory may be gathered by the performance monitor in order to identify performance bottlenecks that are specific to a hardware or software environment.
In addition to the performance monitor described above, an interrupt processing unit may be used to record events such as, for example, instruction execution, branch events, or system events when an interrupt occurs. An interrupt occurs when a device, such as a mouse or keyboard, raises an interrupt signal to notify the processor that an event has occurred. When the processor accepts an interrupt request, the processor completes its current instruction and passes the control to an interrupt handler. The interrupt handler executes an interrupt service routine that is associated with the interrupt. An interrupt may also be caused by a specific machine language operation code, for example Motorola 68000's TRAP, a product from Motorola, Inc. In this case, an unexpected software condition such as divide by zero causes the processor to store the current state, store identifying information about the particular interrupt and pass control to an interrupt handler that handles this unexpected software condition.
However, the performance monitor above must modify the application program at run time in order to record precise performance trace data, such as the number of instructions executed during interrupt processing. Therefore, it would be advantageous to have an improved method, apparatus, and computer instructions for providing pre and post handlers to record precise performance data for events occurring before entering and immediately after exiting an interrupt handler without modifying underlying application program.